idmap_autorid man page

The idmap_autorid backend provides a way to use an algorithmic mapping scheme to map UIDs/GIDs and SIDs that is more deterministic than idmap_tdb and easier to configure than idmap_rid.

The module works similar to idmap_rid, but it automatically configures the range to be used for each domain, so there is no need to specify a specific range for each domain in the forest, the only configuration that is needed is the range of uid/gids that shall be used for user/group mappings and an optional size of the ranges to be used.

The mappings of which domain is mapped to which range is stored in autorid.tdb, thus you should backup this database regularly.

Due to the algorithm being used, it is the module that is most easy to use as it only requires a minimal configuration.

Defines the available matching uid and gid range for which the backend is authoritative. Note that the range acts as a filter. If algorithmically determined UID or GID fall outside the range, they are ignored and the corresponding map is discarded. It is intended as a way to avoid accidental UID/GID overlaps between local and remotely defined IDs.

rangesize = numberofidsperdomain

Defines the number of uids/gids available per domain range. The minimum needed value is 2000. SIDs with RIDs larger than this value will be mapped into extension ranges depending upon number of available ranges. If the autorid backend runs out of available ranges, mapping requests for new domains (or new extension ranges for domains already known) are ignored and the corresponding map is discarded.

Example: with rangesize set to 10000, users/groups with a RID up to 10000 will be put into the first range for the domain. When attempting to map the an object with a RID of 25000, an extension range will be allocated that will then be used to map all RIDs from 20000-29999.

One range will be used for local users and groups and for non-domain well-known SIDs like Everyone (S-1-1-0) or Creator Owner (S-1-3-0). A chosen list of well-known SIDs will be preallocated on first start to create deterministic mappings for those.

Thus the number of local users and groups that can be created is limited by this option as well. If you plan to create a large amount of local users or groups, you will need set this parameter accordingly.

The default value is 100000.

read only = [ yes | no ]

Turn the module into read-only mode. No new ranges will be allocated nor will new mappings be created in the idmap pool. Defaults to no.

This example shows how to configure idmap_autorid as default for all domains with a potentially large amount of users plus a specific configuration for a trusted domain that uses the SFU mapping scheme. Please note that idmap ranges and sfu ranges are not allowed to overlap.